The disease is an eruption of wheals, occurring as an idiosyncrasy in some persons after eating shell-fish, certain fruits, or other food, and almost always dependent upon some gastric derangement. The wheals are indurated elevations of the skin, of varying; size, whitish on the top (the swelling having forced the blood out of the capillaries of the skin),and surrounded hy a reddened zone. They give rise to intense itching, especially when on the covered parts of the body. They appear suddenly and pass away with equal rapidity, one or more crops often coming and going in the course of a single day.